The method and the device are used for blow-molding containers. A preform made of a thermoplastic material is first subject to a thermal conditioning operation along a transport path in the region of a heating section. Thereafter, the preform is formed into the container inside a blowing mold by applying blowing pressure. While the preform is shaped into the container, at least one parameter (49, 50) characterizing the shaping is measured and evaluated by a control unit. Depending on said evaluation, at least one controlled variable (48, 46) influencing the shaping operation inside a closed loop is varied in order to match the measured parameter to an associated target value. In this way, it becomes possible to subject the container parison developing during the blow-molding operation to a predetermined defined development.